Method for producing colored photographs



Patented Apr. 20, 1948 UNITED. STATES oFFicE METHOD FgllitblgjgiglggcOflfifiEb I No Drawing. Application December 27; 1941;

SerialNo.424,574 v 1 Claim.

7 V 1. This invention relates to a method and means for producingcolored photographs.-

He'retofore, it has been the practice to either print a plurality ofdifferently colored images'on separate emulsion layers which were thensuperimposed and registered, or" to: employ special multi -layeredemusicns; Both of these methods,-

however; require the use of relatively expensive,-

spe'c'ial materials such as stripping emulsions in the first method-andmiuti layered. emulsions in these'cond. Furthermoresuch methodsincludedmany elaborate and delicate procedural steps which consume muchtime and require a high degree of manipulative and technical skill.

It is an object of my present invention to overcome the diflicultiesinherent in the foregoing procedures by providing a method whichcomp'rises'relatively few and simple steps, which may bepr'acticed withgood results by persons havingonl y ordinary experience in photography,and which: requires no special materials or apparatus;

Another object of my invention is to provide a method of the characterdescribed, which may layered acromatic emulsion, i. or an emulsion whichis not sensitive to all colors and which:does-- not'include a pluralityof individual layers so arranged and/or constitutedthat each layer isphotosensitive-to a different color. 1

A supplementary object of my invention is to provide chemical reagentsfor successfully practicing my novel method;

Other objects of this invention will: in part be obvious and in parthereinafter'pointed out.

Gertain'features of the invention described but not claimed herein aredescribed and claimed inmy co-pending application for Methods and:means. for producing: a colored photographic image, Serial No. 357,830,filed'septembeit 23, 1940; now Patent No: 2,417,514.

In: general, I practice myinventiorr by succes sively forming a seriesof monochromatic component images of a multichromatic picture ii'f aphotosensitive emulsion The-particular monochromatic componentcolors'employed may con- 2- form with any wen accepted" practice and areso selectedto render afaithful' colored image of the picturebeingreproduced. After each monochromatic compohnt image has actin-ically cf-5. fected the photosensitive emulsionand before the next monoch'o'matic'colored image is projected; the emulsion isdeveloped to bring out acoloredpicture corresponding to the monochromaticcompohentiniage cast.-If'necessary or deny; si rable, the emulsicnis' treated after each butthe last color development toset or preventthe dev'eloped color' imagefrom being affected by any subsequent steps my process and" particularlyby an y'suhseduent"stepsinadeveloping further col- 1'5 orst SificethisIast step-tends to reduce the photosensitivity'oi the silv alts, -Ipreferably treat the emulsicm after" or" during-such setting step toofi'set such decreased sensitivity and to substantially orpantialiyrestore said emulsion to its 2 original state orphotosensitivity. All of the monochromatic component images areprojected in're'g-istry upon: the-same single photosensitive emulsion. Iformed 1 Who-photosensitive emulsion; any suit- 25 able method fordeveloping colors may beemployed." The emulsion' is not exposed toactinic rays,- except when m'odulated bypolor component images, untilall the colors havebeen developed. It will thus be apparent that afterall of the 30 monochromatic component images; such as for exampleblu'e',- red and yellow, have been separately projected upon anddeveloped inthe photose'nsiti ve emulsion; the original coloredepicturewill be exactly reproduced in filll color in the single layer ofphotosensitive emulsion.

I prefer: to carry out my invention by using a dye-coupling 5 developing1 process-,- such as described in: aforesaid co'pendihg application, andwhemsuch method of color developing is employed; thefollowin'g steps; ingeneral, are performem First, black" and white color separationnegatives are made: the: usual manner from a colcred picture ortransparency," asby employing 4'5 coloredfil'ters. Afterprepari-ngsuchnegatives, actinlc printing light is passedthroughone of the negativesforexarhple, the blue one, and

projected upon the surface of the photosensitive emulsion. 'Ihe'exposure of the photosensitive emulsion may he: perform-sa nt anystandard a paratusgsuch: aster exampleflan enlarger or a contactprimer,- Whe-n b ckand white color separatiomnegatives are ploy e'd w hthe usual white; printing: light," ei th 1' achromatic or Dan 55-chromaticemulsions may-he used. However, I

n; develbping the" latent images- 3 prefer achromatic emulsions, sincered light may then be present in the developing room and the course ofthe development closely observed. If panchromatic emulsions are used,color separation negatives may be dispensed with, and in lieu thereofmonochromatic beams of light successively reflected from or passedthrough the col= ored picture to be reproduced andthen projected uponthe emulsion. Themonochro'm'atic beams employed may correspond to themonochromatic component colors used to form the color separationnegatives. are employed, all treatments subsequent to formation oflatent images are similar to the treatments of achromatic emulsions.

ponent color of the picture being reproduced has been formed in thephotosensitive emulsion, said image is developed by reduction. Astandard non-coupling developing agent may be used, such as for examplemetol, whose properties in connection with color developing bydye-coupling are fully set forth in my copending application. While theimage is being reduced, it is simultaneously treated with acoupling-inducer, which may be of a reducing nature, and a color-couplerwhich corresponds to the color component of the first or bluenegative-separation image. Any standard coupling-inducers andcolor-couplers well known to the artmaybe employed in the process hereindescribed.

When panchromatic emulsions.

1 After a latent image corresponding to a com 4 methylenetetramine.Where the salting reagent is alkaline in nature, as for example in thecase of sodium carbonate, it is desirable to add a mild or very diluteacid or an acid salt, as for example phosphoric acid, citric acid,tartaric acid, dilute acetic acid (one part in ten thousand) or sodiumacid phosphate. These acidifying reagents reverse the alkalinity of theemulsion caused by the developing bath. It will be appreciated that thestandard salting reagents are always used with a reagent for hardeningthe gelatin or with a reagent which will react with the salting reagentto produce a compound which will harden the gelatin. Examples of suchhardening reagentawhich, it will be seen, include some of the settingreagents above set forth, comi |prise formaldehyde, alums such as chromealum Since the same photosensitive emulsion. is-to be treated in severalreducing and, coupling baths, I preferably employ means to prevent toogreat a softening of the emulsion and also to prevent fogging, whichmight be incidentto treatment in three separate developing baths. ,Theanti-softening or hardening reagent employed may be any suitablegelatin-hardening substance, as for example an alkali metal sulphate. Inconjunction with the hardeningreagent, it is also desir-. able to useastrong accelerating agent in the developing bath. An example of such.an accelerating agent is sodium hydroxide. The combination of astrongaccelerator anda hardener I have found prevents staining oftheclear portions of the film and prevents; too great a softening of thegelatin emulsion. r Y

Owing to the fact that after onecolor has been coupled the emulsion is,atalater stage here-.

formate. These setting reagents can be used in-.

dependently or in combination, and highly :satis-'- factory results havebeen obtained when sodium formate is used with one ;or more of the otherreagents.

If desired, there may also be employed standard salting reagents in thesetting solution to better precipitate, the colors, These reagents,however, must not affect the photosensitive silver salts. By way ofexample, such reagents may comprise sodium carbonate, ammonium sulphate,sodium phosphate, calcium acetate, and hexaor potassium alum,paraformaldehyde, tannic acid, sodium sulphate, magnesium sulphate, andphthallic anhydride. In the foregoing list, the phthallic anhydriderepresents an example of a compound which will react with the saltingreagent, hexamethylenetetramine to produce or free a substance,formaldehyde, for hardening the gelatin emulsion.

It will thus be seen that the bath in which the emulsion is treatedsubsequent to the first developing preferably contains reagents toperform the following functions: setting, salting, acidifying andhardening. However, it is not necessary to have a separate reagent foreach of these stated functions, as one reagent may serve to perform twoor more, such functions.

The setting and hardening reagents tend to decrease the sensitivity ofthe emulsion towards futureexposures, and to offset such desensitizationI may provide a reagent which inhibits the desensitizing effect of thesetting reagent or which resensitizes the emulsion. An example of areagent which offsets thev efiect of the setting reagent is potassiumferrocyanide. This-latter reagent greatly decreases the exposure timerequired to form latent images of color separation negativessubsequentto development of the first color separation image. It may be noted thatwhere a chrome alum and sodium formate setting bath is employed, thetime of exposure for thenext negative is twenty times as great as whenno such setting bath is employed. But if after treatment with suchsetting bath, I submerge the emulsion in a ferrocyanide bath, the timeof exposure required for future negatives is considerably reduced.

-Other examples of desensitizing-inhibiting or resensitizing reagentscomprise certain salting reagents, including the halide salts of metalsor-positive radicals'which do not detrimentally affect thephotosensitive silver halides. Examples of such salting reagents areammonium, lithium, strontium and nickel halides. The halides which- Ipreferably use are bromides and chlorides, although other halides maybeemployed to attain certain color effects. not ordinarily desired. I havefound the halides restore the sensitivity of the set emulsion to a muchgreater degree than the ferrocyanide, and the emulsion by such treatmentmay be rendered even more sensitive than before exposure. 7

It may be mentioned that the'desensitizinginhibiting or resensitizingreagent may be present either in the setting bath or in a separate bath,

' although I prefer-to place such reagent in the setting bath;

After the first or blue monochromatic colored image is set,-the emulsionis washed. It is then aasaeor:

placed in the enlarger or-contact printer in the same position: that itoccupied during the first exposure, and exposed to a printing lightmodulated by a second color separation negative, for example/red- Thered separation negative occupies exactly the same position as the firstor blue separation negative; Thisexposure will cause the formation of'asecond latent image in the emulsion. Siaidv image is reduced and coupledto bring out a monochromatic picture correspending in color to the colorof the second separation negative. This second picture is set and theemulsion treated in a sensitizing or desensitiZation-inhibiting bath.After washing, the emulsion is returned for printing with a third oryellow separation negative. The latent image formed is developed andcoupled to bring out the third color component which does not have to beset since no further developing treatments are to be performed upon theemulsion.

At this time, the emulsion, if properly exposed and developed inconnection with each of the three colors, presents a faithfully coloredreproduction of the original image; and the emulsion' can now be stoppedin a hypo solution. If the emulsion is to be used as a motion picturepositive, the process may be halted at this stage. If, however, theemulsion is to be used as a positive. print on paper, it is alsodesirable to bleach out. the reduced silver grains. This isaccompli'shed. by treatment in the usual bleaching baths of the art.

I have found it desirable to first expose the emulsion to a blueseparation negative, then to ared separation negative and finally to ayellow separation negative. This order of exposure and development isparticularly effective where an achromatic photo sensitive emulsion isemployed.

It may be mentioned that after the yellow color development, thereproduction may be examined. for yellow color tone value and that theyellow may be varied in intensity if necessary before stopping theemulsion in hypo.

By way of example, I have set forth below various specific chemicals andprocedural steps which are employed in carrying out my invention. Thesechemicals and steps have been found to. give highly satisfactoryresults. It is to be understood, however, that the examples are in noway to be considered limitative.

Example I First, blue, red and yellow separation images ot the pictureto be produced are prepared. The blue separation negative is then placedin position in an enlarger. A sheet of ordinary achromatic silver halideprinting paper is wetted, as for example in water, and then also placedin the enlarger, the negatives and printing paper being positioned inthe usual manner so that a beam of.

white printing light modulated by the blue negative will be projectedupon the paper. The wetting step is performed in order to swell thepaper fibres, thereby placing the paper in the same condition that itwill be in during subsequent printing steps and ensuring registration.The source of light in the enlarger is now energized and the paperexposed for a suificient period of time to form a latent image therein.This period of exposure will vary with the type of printing paperemployed and with the density of the picture to be reproduced. Forconvenience, the blue exposure period will be denominated as one unit ofexposure value. r

After exposure, the paper, having the latent a bath prepared accordingto the following instructions:

The developing bath is formed by mixing together several stocksolutions. Stock solution A is prepared froma dry powder including thefollowing substances in the specified proportions by weight:

' Grams 2-4 dichloro-l naphtol 4 Sodium sulphite ll) Sodium acidphosphate 1 One gramof the dry powder is dissolved in 15 cc. of acetoneand 50' cc. of water. Such a stock solution is good for approximatelyone week.

Stock solution B is prepared. from a dry powder including the followingsubstances in the specified proportions by weight;

Grams Para aminodiethylanalinemonohydrochloride 3 Metol 1 Sodiumsulphite l5 Onegram of the dry powder is dissolved in 50 cc. of water.This stock solution will last indefinitely.

Stock solution C is preparedjfrom a dry powdcr including the followingsubstances. in the specified proportions by weight:

Grams Sodium borate 6 Sodium sulphate 4 Sodium hydroxide 40 One gram ofthe dry powder isdissolved in 5000. of water. This stock solution willlast indefinitely.

Stock solution D is prepared from a dry powder including the followingsubstances in the specified proportions by weight:

grams Sodium formate 4 Potassium ferrocyanide 1 Five grams of the drypowder is dissolved in cc. of water. This stock solution will lastindefinitely.

The sodium formate and: potassium ferrocyahide in the dry powder are notmerely mixed together, but these substances are dissolved andsubsequently recrystallized soas to increase the solubility of theferrocyanide and thereby render the process more easily practiced byamateurs.

The developing solution. is. prepared by mixing together:

Stock solutionA cc-.. Stock solution B cc Stock solution C 00.. Stocksolution D cc Water 00.. Ten percent water solution of potassium bromidedrops 2 in a setting solution wherein it is moved around for about oneminute. The temperature of the setting solutionis maintained at about 65to 68 F. The setting solution is prepared by mixing together;

percent of water solution of chrome The next step comprises washing thesheet in running water from three to five minutes. Finally, the sheet issqueegeed.

The damp sheet is then returned to the enlarger and exposed to aprinting light modulated by the red separation negative for a period oftime substantially equal to four units of exposure value to form a redcomponent latent image in the emulsion. This image is developed byimmersing the sheet in a red coupling and developing bath prepared asfollows:

A stock solution E is made from a dry powder including the followingsubstances in the specified proportions by weight:

grams Para-nitrophenylacetonitrile 1 Sodium acid phosphate 1 Sodiumsulphite 5 One gram of the dry powder is dissolved in 15 cc. of acetoneand 50 cc. of water. This solution is good for about one week. The reddeveloping solution is similar to the blue developing solution, exceptthat cc. of solution E is substituted for 10 cc. of solution A.

The duration of developing and the temperature of the red developingbath are the same as when developing the blue component image. Afterdeveloping, the sheet is washed, set, washed and squeegeed as describedwith reference to the blue image.

Now the sheet is again replaced in the enlarger and this time exposed toa printing light modulated by the yellow separation negative. Theprinting time for the yellow negative is twelve units of exposure value.The yellow component latent image thus formed on the sheet is developedin the same manner as the red and blue images. However, 10 cc. of stocksolution F replaces solutions A and E.

Said stock solution F is prepared from a dry powder including thefollowing substances in the specified proportions by weight:

grams Aceto 2-5 dichloroanaline 6 Sodium sulphite 4 Sodium acidphosphate 1 One gram :of the dry powder is dissolved in cc. of acetoneand 50 cc. of water. This solution will last for long periods of time.

The sheet is now washed in running water for one minute, but thetreatment in the setting bath is omitted.

The sheet is next desensitized in a hypo bath. For this purpose, thesheet is immersed in the hypo bath for two minutes while the bath ismaintained at a temperature of from about 65 to 68 F. The hypo bath isthe standard one prepared by adding two pounds of sodium hyposulphiteand five grams of sodium bisulphite to one gallon of water.

While the print is still wet with hypo solution, it is immersed in ableaching bath to remove the reduced silver grains. The bleaching bathis a one per cent water solution of potassium ferricyanide. The print isleft in the bleaching bath for from 45 seconds to 2 minutes while thebath is maintained at a temperature of from about to 68 F. This bathwill remove all reduced silver.

The yellowish stain left by the ferricyanide bath is removed byreturning the print to the hypo bath and leaving same there for aboutone minute.

Finally the print is washed in running water for from five to eightminutes, squeegeed for finish and dried.

Example II grams Potassium alum 25 Sodium for-mate 25 Fifty grams of thedry powder is dissolved in 1,000 cc. of water. This solution will lastindefinitely.

Stock solution H is prepared by adding five grams of ammonium bromide to100 cc. of water. This solution will also last indefinitely.

100 cc. of stock solution G is mixed with 10 cc. of stock solution H toform a setting bath which also includes a silver halide sensitizingreagent. When halides are employed in a setting bath, the red separationnegative needs only to be exposed for one and one-half units of exposurevalue and the yellow separation negative for three units of exposurevalue.

The emulsion sheet is left for about one and one-half minutes in theabove bath which is maintained at a temperature of from about 65 to 68F.

Example III Where it is desired to employ a. salting reagent whichreacts withanother compound to produce a hardening reagent in thesetting bath, the following solution may be employed in lieu of thesetting solution given in Example I:

Solution I is prepared by dissolving two grams of phthallic anhydride in100 cc. of boiling water. While the water is still hot, five grams ofhexamethylenetetramine is added. The solution is now allowed to cool andanother 100 cc. of water is added. This solution will last indefinitely.

Solution J is prepared from a dry powder including the followingsubstances in the specified proportions by weight:

Grams Ammonium bromide 5 Ammonium chloride 5 Five grams of the drypowder is dissolved in 100 cc. of water. This solution will lastindefinitely.

cc. of solution I is added to 20 cc. of solution J to form a settingbath. It will be noted that this bath includes a halide reagent. Thebath is used at a temperature of from about 65 to 68 F. at which theemulsion is treated for about one to one and one-half minutes.

It will thus be seen that there is provided methods and means by whichthe several objects of this invention are achieved, and which are welladapted to meet the conditions of practical use.

As various possible embodiments might be made of the above invention,and as various changes might be made in the embodiments above set forth,it is to be understood that all matter herein set forth is to beinterpreted as illustrative and not in a limiting sense.

Having thus described my invention, I claim as new and desire to secureby Letters Patent:

A method of producing a colored photograph of a multichromatic picturein a single-layered emulsion having photosensitive particles distributedthroughout, comprising successively forming registered latent images ofdifi'erent monochromatic components of said picture in said emulsion bysuccessively casting on one side thereof beams of light modulated bydifferent color components of said picture and, prior to forming eachlatent image, subsequent to the first latent image, color developing thepreceding latent image by dye-coupling, disturbing the capacity of thecoupled dye to unite with chemicals subsequently used for forming othercoupled dyes Without aifecting any previously actinically affectedphotosensitive particles, and offsetting the decreased photosensitivityof said photosensitive particles resulting from such disturbance, saiddisturbance and ofisetting of the decreased photosensitivity beingefiected by treating the emulsion in a, bath includinghexamethylenetetramine, phthallic anhydride and a halide.

HENRY T. NEUMANN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,207,527 Fox Dec. 5, 19161,710,455 Langguth et a1 Apr. 23, 1929 10 1,963,197 Froehlich June 19,1934 1,968,956 Murray et a1 Aug. 7, 1934 1,976,301 Seymour et al. Oct.9, 1934 2,059,887 Mannes et a1, Nov. 3, 1936 2,151,532 Schmidt et alMar. 21, 1939 15 2,198,827 Leuch 1 Apr. 30, 1940 2,200,018 Bertrand May7, 1940 2,244,589 Yanket June 3, 1941 FOREIGN PATENTS 20 Number CountryDate 404,856 Great Britain Jan. 25, 1934

